The present invention relates generally to diving systems and more particularly to self-contained underwater re-breathing apparatus.
Self-contained underwater re-breathing apparatus or rebreathers are well known in the art. As the name implies, a rebreather allows a diver to xe2x80x9cre-breathexe2x80x9d exhaled gas. Rebreathers consist of a breathing circuit from which the diver inhales and into which the diver exhales. The breathing circuit generally includes a mouthpiece in communication with an inlet to and outlet from, a scrubber canister for scrubbing CO2 from the exaled gas. At least one variable-volume container known as xe2x80x9ccounterlungxe2x80x9d is incorporated in the breathing circuit. Exaled gas fills the counterlung. Diver""s inhalation draws the exaled gas from the counterlung through the scrubber canister. CO2-depleted gas from the scrubber canister is fed again to the mouthpiece and the diver""s lungs.
A typical rebreather further includes an injection system for adding fresh breathable gas from at least one gas cylinder to the breathing circuit. It is vital to provide proper physical parameters (such as partial pressure of oxygen or PPO2) of the breathing gas mixture inside the breathing circuit in accordance with pressure (determined by the depth of diving). This can be achieved by controlling said injection, which can be operated manually or automatically. In simple cases, that is small and constant depths, manual control can be employed, usually limited to adjusting a regulator for feeding breathable gas to a predetermined PPO2. More or less complex diving profile at substantial depths requires automatic control.
Thus, up-to-date rebreathers usually have an automatic control system including a microcomputer for monitoring physical parameters in the breathing circuit and controlling the feeding of breathable gas to the breathing circuit in accordance with said physical parameters.
It can be seen that a rebreather is a complex system incorporating a good deal of automation. Meanwhile, it is well known that failure is more probable for a complex system. Thus, a need exists for a reliable bailout system capable, in an emergency, of supporting the diver""s life until he gets back to the surface and can breathe in atmospheric air.
An attempt to add an open-circuit bailout to a closed-circuit rebreather was made in U.S. Pat. Nos. 4,964,404 and 5,127,398 by Stone. In the event of closed-circuit malfunction, the user can manually switch a valve incorporated in the mouthpiece to shut off the closed circuit and open a direct communication with a diluent supply to allow the user to exale directly therefrom.
The key element of the system invented by Stone is a mouthpiece which is excessively large and rather complex, as seen from U.S. Pat. No. 5,127,398. In fact, in the mouthpiece two independent breathing circuits meet, and means for switching from one breathing circuit to another are provided. A diver may feel uncomfortable having a mouthpiece as large as this in front of his face, and his field of view is confined.
Further, it does not always happen that a diver facing an emergency situation under water keeps cool and performs necessary actions such as switching a regulator in the mouthpiece. Therefore, it would be desirable to automate the switching to the open-circuit bailout. However, to achieve this with a prior art rebreather such as Stone""s it would be necessary to add to the mouthpiece a solenoid and take a waterproof electric wiring thereto. This would make the mouthpiece even more large and complex.
It is an object of the present invention to provide a self-contained underwater re-breathing apparatus, which supports diver""s life in the event of an emergency.
A further object of the present invention is to provide a self-contained underwater re-breathing apparatus with a bailout system which is able to automatically switch to open-circuit breathing, wherein a large and complex mouthpiece is not needed.
A further object of the present invention is to provide a self-contained underwater re-breathing apparatus with a bailout system which does not require performing any actions from the diver.
These objects are achieved by providing a self-contained underwater re-breathing apparatus comprising a breathing circuit including a mouthpiece having an outlet for exaled gas and an inlet for inhaled gas, the breathing circuit further including at least one variable-volume container incorporated therein and a scrubber for scrubbing CO2 from exaled gas, the scrubber having an inlet and outlet in communication with the first mouthpiece outlet and the mouthpiece inlet, respectively, the re-breathing apparatus further comprising a first breathable gas cylinder in communication with the breathing circuit through a pressure differential control valve, a shut-off valve in the breathing circuit upstream the control valve, an automatic control means comprising sensors for monitoring physical parameters in the breathing circuit, the automatic control means being adapted to close the shut-off valve when abnormal parameters are detected by the sensors, and a second breathable gas cylinder in communication with the breathing circuit through an automatic control valve controlled by the automatic control means; wherein the breathing circuit further comprises an exhaust valve for exhausting exaled gas when the shut-off valve is closed.
With the system of the invention, a part of the existing closed circuit is used for bailout, and no separate bailout circuit is provided. Therefore, there is no need to incorporate in the mouthpiece means for switching from one breathing circuit to another, and the mouthpiece can be kept smaller and simpler. Further, switching to bailout is fully automated, so that no actions are required from the diver.
Preferably, the opening pressure of the release valve is adjustable.
Preferably, the first breathable gas cylinder contains diluent gas, and the second breathable gas cylinder contains oxygen.
The control valve can be a pressure differential control valve.
Preferably, the exhaust valve is incorporated in the mouthpiece.
A means for shutting off the breathing opening can be provided in the mouthpiece.
More specifically, the mouthpiece can have a cylindrical rotatable insert having an opening and fixed to a stub tube extending outside, wherein by rotating the insert, its opening can either be aligned or misaligned with the breathing opening.
Said insert is can be rotated manually by acting on the stub tube, into which the exhaust valve is preferably incorporated.